Lever

ABSTRACT

A lever, for example, for transferring force to another structural component of a mechanism, has a prefabricated connecting piece disposed on at least one of its ends. The lever is constructed as a hollow profile made of material that can be shaped without cutting. The hollow profile forms a receiving chamber on at least one end for the prefabricated connecting piece. The walls of the receiving chamber rest tightly against the circumference and the end faces of the connecting piece.

BACKGROUND OF THE INVENTION Field of Invention

The present invention relates to a lever, having at least one connectingpiece for connecting to the other parts of the mechanism.

Levers are used in a wide variety of forms for transferring force, forexample in coupling mechanisms, pivoting levers, and as fastening leversfor connecting to driven shafts. In motor vehicles, they are used amongother things for driving windshield wipers. Frequently, they areconstructed of a support profile that is U-shaped in the center which,on its flat ends, has connecting pieces in the form of sockets that arecast into bores by means of injection molding. The sockets are supportedon a small surface which is essentially produced by the narrow wallthickness or material thickness.

Levers for windshield wipers are already known which are made of zinc ora zinc alloy by means of diecasting in a diecasting form (DE 44 44 328A1). Each lever has a conical hub on its one end, which can be connectedto a likewise conical axle. A reinforcing element is provided in thevicinity of the hub and is cast into the lever like a core. It is costlyto manufacture levers of this kind.

The periodical “Werkstatt und Betrieb” [Workshop and Operations], KarlHanser Verlag Munchen, 1995, pp. 812 to 815 and the reprint from theperiodical “Metallumformtechnik” [Metal Shaping Technology], ClausDannert Verlag, 1994, under the title “Präzisions-Werkstücke inLeicht-bauweise, hergestellt durch Innenhochdruck-Umformen”,[Lightweight Precision Work Pieces Produced by Means of InternalHigh-Pressure Shaping] have disclosed a process for shaping pipes intowork pieces. This process, which is primarily used for the automotiveindustry, works with high pressures.

The pipe section to be shaped is inserted into a split tool which hasthe desired work piece form incorporated into it. The tool, which ismounted in a press, is closed by means of a vertically functioning pressram. The pipe section ends are closed in a sealed fashion by means ofclosing tools through which a pressure medium is supplied which pressesthe pipe walls against the interior of the tool form. At the same time,horizontally acting rams exert an axial pressure onto the pipe section,which superposes the internal pressure. Consequently the material whichis required for the shaping is not only taken from the wall thickness ofthe pipe section, but is also supplied by the shortening of the pipe.The closing tools are axially guided toward each other during theshaping.

BRIEF SUMMARY OF THE INVENTION

According to the invention, the lever has a hollow profile made ofmaterial that can be the shaped without cutting, which on at least oneend constitutes a receiving chamber for a prefabricated connectingpiece. The walls of the receiving chamber rest tightly against the endfaces and the circumference of the connecting piece so that it isencompassed by two opposing walls of the hollow profile in a secure,uniform, captive fashion. The contact faces between the walls of thehollow profile and the connecting piece are independent of the wallthickness and fulfill the requirements for a uniform force introductionand favorable force transfer. Furthermore, the connecting piece fitsharmoniously into the contour of the lever.

Depending on function, the connecting pieces can be differently embodiedso that a multitude of lever variants can be produced with the samehollow profiles and different connecting pieces. Thus, the connectingpieces can have a bearing bore for a pivoting bearing, a socket for aball-and-socket joint, or threaded bore for a fastening screw. Thebearing bore can also be used as a through bore for a fastening screw.

In order to enlarge the contact surfaces between the connecting pieceand the walls of the hollow profile, it is suitable that the connectingpiece has a collar against which the walls of the receiving chamber arepressed. The collar is simultaneously used for better alignment of theconnecting piece to the hollow profile and gives it a more stableposition. This is further encouraged by virtue of the fact that thethickness of the collar increases toward the outer circumference so thatan undercut is produced toward the inside into which the walls of thereceiving chamber are pressed.

In order to align the connecting piece before the pressing procedure andto secure it temporarily in the receiving chambers, it is suitable thatthe receiving chambers have pre-formed beads toward the center part ofthe hollow profile, against which the connecting piece can be laid andbetween which it can be slid or clamped with its collar.

According to other embodiments of the invention, form fitting elementsare provided which produce a positive fit between the connecting pieceand the receiving chamber in the circumference direction of theconnecting piece. This is advantageously achieved by virtue of the factthat the connecting piece or its collar has one or a number of recesseson its end face or circumference, into which the walls of the receivingchamber are pressed or caulked. Furthermore, the cross sectional contourof the connecting piece can have a shape which diverges from that of arotational body, for example a polygon or oval. In many instances, aflattening on the circumference sufficiently secures the connectingpiece against rotation.

Depending on the intended use, it can be desirable that the connectingpieces are open toward both sides or only open toward one side. Thesetwo variants can be simply covered according to the invention by virtueof the fact that the receiving chamber of the hollow profile in oneinstance has two opposing connecting openings and in the other instancehas only one connecting opening. In the second instance, largely closedand therefore protected pivoting bearings can be simply produced withthe same connecting pieces.

The levers with a hollow profile have a greater torsional rigidity sothat the wall thickness in relation to open profiles can be reducedwhile maintaining the same torsional and flectional rigidity. Thisresults in a lower consumption of material and a reduced weight.Furthermore, sharp edges are largely prevented by means of the hollowprofiles and therefore the danger of injury is practically eliminated.

The hollow profile is suitably produced using an internal high-pressureshaping process in which a pipe section is inserted into a split toolform and the pipe ends are closed by means of sealing tools. Then thetool form is closed and pressure fluid is supplied by way of the sealingtools, so that the internal contour of the tool form with the hollowspaces for the hollow profile with the receiving chambers is formed bymeans of the pressure increase. The pipe ends are suitably slid towardeach other axially with the sealing tools. Consequently, an axialpressure is exerted on the pipe ends during the shaping and uniform wallthicknesses and precise contours are produced, which require little orno mechanical finishing work.

Then the part is removed from the tool form and the required connectingopenings are let into it. After this, the connecting pieces are insertedinto the receiving chambers and the walls are placed against theconnecting pieces in particular by means of pressing or wobble forging.Wobble forging is a process in which a press tool executes a wobblingmotion around the advancing axis during the pressing process, by meansof which the pressing forces can be reduced.

The process according to the invention permits a flexible formembodiment so that even in a complex version, levers can easily beproduced which make favorable use of the available space. Levers with awide variety of hollow profiles both in the longitudinal direction andin the lateral direction can therefore be produced, which fulfill a widevariety of requirements with regard to space, torsional rigidity,flectional rigidity, and noise production in accordance with theintended use.

The process advantageously uses low-strength galvanized steel pipe or apipe made of an aluminum alloy. They are sufficiently pourable andcorrosion resistant and do not need to be subsequently treated. Inaddition, aluminum alloys also have other weight advantages. Bothweld-free and longitudinally welded pipes are used.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages ensue from the following description. Exemplaryembodiments of the invention are shown in the drawings. The drawings,the description, and the claims contain numerous features incombination. One skilled in the art will also suitably take the featuresinto account individually and will combine them into other logicalcombinations.

FIG. 1 shows a longitudinal section through a lever according to theinvention,

FIGS. 2 to 8 show an enlarged, partial, longitudinal section through anend region of a lever or a connecting piece in various embodiments,

FIGS. 9 to 10 show a top view of a connecting piece in variousembodiments, and

FIG. 11 shows a schematic longitudinal section through a tool form forproducing a lever according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The lever 10 according to FIG. 1 is a pivoting lever with a hollowprofile 12, which constitutes receiving chambers 14 on its ends (FIG. 2)into which connecting pieces 16 are inserted through openings 74.Depending on the flectional stress, the cross section of the hollowprofile 12 increases toward the center of the lever 10.

The connecting pieces 16 have a collar 18 on their circumference whosethickness increases toward the outside so that an undercut is producedinto which walls 26 and 28 of the receiving chamber 14 are pressed. Thewalls 26 and 28 consequently rest in a large contact area against theend faces of the connecting piece 16, against its circumferencesurfaces, and against the collar 18.

FIG. 2 shows the connecting piece 16 before the pressing process. Inorder to align it in relation to the hollow profile 12 and to secure ittemporarily, pre-formed beads 22 are provided on the hollow profile 12toward the center part, against which beads the connecting piece 16rests and between which the collar 18 is secured. The result of thepressing procedure is the finished lever according to FIG. 3. Thepressing direction is labeled 24. The connecting pieces can be embodiedin different ways. While the connecting pieces 16 and 38 have a socket20 for a ball-and-socket joint, a connecting piece 42 (FIG. 6) has abearing bore or through bore 40, a connecting piece 46 (FIG. 7) has athreaded bore 44, and a connecting piece 48 (FIG. 8) has a bore with aslaving profile 50.

Furthermore, the connecting pieces can have different rotationprevention means. The connecting piece 38 therefore has a recess 34 onone end face and a recess 36 on its collar 18. The wall 28 is pressedinward or caulked into the recesses 34 and 36 (FIG. 5) so that theconnecting piece 38 is prevented from rotating in relation to the hollowprofile 12. The recesses 34 and 36 can be used individually or jointlyand can be affixed to one end face or to both end faces. Correspondingrecesses can also be provided on the circumference surfaces of theconnecting piece 38. The connecting piece 52 has a cross sectionalcontour 54 in the form of a polygon, which deviates from a rotationalbody. A cross sectional contour of this kind can also be disposed on thecollar 18. FIG. 10 shows a connecting piece 56, which has a flattening58 on the circumference, which is used as a rotation prevention means.

In the vicinity of the connecting pieces 16, 38, 42, 46, 48, 52, 56, thereceiving chamber 14 has at least one connecting opening 30, 32.Consequently, levers 10 can be produced which have connecting openings30 and 32 disposed opposite each other (FIG. 2, FIG. 3) and levers 10can also be produced which have only one connecting opening 30 and areotherwise closed (FIG. 4, FIG. 5).

The lever according to the invention and the process for manufacturingit consequently cover a multitude of embodiments with simple means.

In the example by hollow profile 12 with two receiving chambers 14 onthe ends, FIG. 11 shows a schematic longitudinal section through a toolform 60 for the internal high-pressure process. A pipe section 66 isinserted into a split tool form 60 with a top piece 62 and a bottompiece 64. The pipe ends are closed by means of sealing tools 68. Apress, not shown, closes the tool form 60. The pipe section 66 canalready be pre-formed in this connection. It is also possible to useotherwise pre-formed pipe sections 66. This is particularly suitable formore complex forms.

Pressure fluid at high pressure is pressed into the pipe section 66through bores 70 in the sealing tools 68 so that the pipe section 66rests against the internal contour of the tool form 60 and takes shape.Then the hollow profile 12 is removed from the tool form 60. Theconnecting openings 30 and 32 as well as the opening 74 are produced,for example, by means of removing a part of the pipe section 66 or byboring or stamping.

The pipe section 66 can be comprised of all kinds of materials. Alow-strength galvanized steel pipe has turned out to be particularlyfavorable; but pipe sections 66 made of an aluminum alloy are veryadvantageous because of their low weight and their favorable corrosionresistance.

In order to produce the most uniform wall thicknesses possible, duringthe shaping of the pipe section 66 the pipe ends are suitably slidtoward each other with the sealing tools 68 in the direction of thearrows 72. As a result, the material for the shaping of the hollowprofile 12 is taken not only from the wall thickness of the remainingpipe section 66, but is also supplied by the shortening of the pipesection 66.

We claim:
 1. A process for producing a lever (10) which has at least oneprefabricated connecting piece on at least one end, and a hollow profileconstituting a receiving chamber on at least one end for receiving theconnecting piece so that two opposite walls of the receiving chamberrest tightly against a circumference and end faces of the connectingpiece comprising the steps of: inserting a pipe section (66) into asplit tool from (60); closing the pipe ends by sealing tools (68);closing the tool form (60); supplying pressure fluid by means of atleast one sealing tool (68); shaping an internal contour of the toolform (60) with hollow spaces for the hollow profile (12) and at leastone receiving chamber (14) by means of pressure increase; removing thehollow profile (12) from the tool form (60) and opening the at least onereceiving chamber (14) formed; inserting the at least one prefabricatedconnecting piece (16) into the receiving chamber (14) and pressing theconnecting piece with the receiving chamber; and the two connectingpieces (13) are inserted into the two receiving chambers 14 and theopposing balls (26, 28) of the receiving chambers are placed againstcollars of the connecting pieces by wobble forging.
 2. The processaccording to claim 1, wherein a low-strength galvanized steel pipe isused as the pipe section (66).
 3. The process according to claim 1,wherein the pipe section (66) is made of an aluminum alloy.
 4. Theprocess according to claim 1, wherein during the shaping of the pipesection (66), the pipe ends are slid toward each other with the sealingtools (66).
 5. The process according to claim 1, wherein connectingopenings (30, 32) are produced by stamping.
 6. The process according toclaim 1, wherein connecting openings (30, 32) are produced in asubsequent work cycle.
 7. The process according to claim 1, wherein byusing the internal high-pressure shaping process, beads (22) arepreformed into the opposing walls (26, 28) of the receiving chambers(14) toward a center part of the hollow profile (12).